In conventional train radio systems, an on-board control device in a train detects the position of the train and the train position information is transmitted to the train-presence management device on the ground via a train control radio base station. The system on the ground side uses the train position information on each train to calculate the stop limit position, and the like for each train and transmits the calculated results to the trains via the train control radio base station, thereby managing the operations of each train. Such a technology is disclosed in Patent Literature 1 described below.